The present invention, relates to traction units for vehicles.
The present invention, more particulary, relates to a belt-type traction unit, trained around the tire of a farm tractor, or other vehicle, designed to increase the traction surface area in contact with the ground surface, thereby enabling the vehicle to move more easily on snow, sand, or other soft terrain, that normally prevents movement of conventional wheeled vehicles.
The present invention, most particularly, relates to vehicle motion in deep snow, although the principles of the present invention could also be applied to vehicles being operated in other types of terrain.
It is already known to increase the ground traction surface area of a vehicle tire, by running an endless belt traction unit around the tire, and auxiliary bogie wheels, or another tire.
U.S. Pat. No. 3,860,080, issued to Harold Firstenberg, on Jan. 14, 1975, shows an endless belt system, trained around a vehicle tire, and six auxiliary bogie wheels, located to the left, and to the right, of the tire, as seen in FIG. 1 of the patent. The system is believed to be overly complex, in that a relatively large number of bogie wheels is required.
Also, in the Firstenberg system, the belt mechanism is formed by four separate V-belts, interconnected by a series of transverse grouser bars, or cleats. Should the tension forces, or slack, differ appreciably in the different V-belts, the grouser bars will, inevitably, have skewed positions that can produce high angular loadings, and detachment of the bars, from the V-belts.
Further, in the Firstenberg system, the bogie wheels are located in planes, offset from the plane of the vehicle tire, such that the overall width of the system is, necessarily, rather large, i.e., almost four (4) times the tire width. Each bogie wheel has a V-shaped cross-section, for tracking on one of the V-belts. Should the V-groove in a wheel become clogged with dirt, debris, or .ice, the bogie wheel would, most likely, disconnect from the V-belt, or generate an abnormal tensile stress on the belt.
A further problem with the Firstenberg traction unit is that a relatively costly and complicated adjustment device is used, for controlling the slack, or tension, in the various V-belts. Two gear-like rollers are carried on swingable arms, for engagement with the transverse cleats that span the various V-belts. Tensioned cables extend from the swingable arms, around a central winch mechanism, such that manual rotational adjustment of the winch can, theoretically, be used to adjust the cable tension, and the forces exerted by the gear-like rollers, on the transverse cleats. The mechanism is seen to be rather cumbersome, costly, and prone to failure.
The present invention is directed to a belt-type traction unit, designed to be much simpler, and more rugged, than the unit disclosed in the Firstenberg patent.
U.S. Pat. No. 3,561,825, issued to D. Gibson, et al., on Feb. 9, 1971, discloses a belt-type traction unit formed by two laterally spaced flat belts and a large number of transverse grouser bars. The belt system is trained around two vehicle wheels, arranged in tandem, i.e., one behind the other. The tread surfaces on the vehicle tires engage the grouser bars, but, apparently, not the belts. The belts, apparently, only serve as connection devices for the ends of the grouser bars. The grouser bars are driven, in an endless path, by means of a rotary sprocket wheel, located above the belt system, midway between the two vehicle wheels.
The mechanism proposed in Gibson et al., appears to be usable, only with specialized vehicles, having tandem wheels, and a special drive sprocket, located midway between each pair of wheels. The Gibson et al., mechanism could not be used as an add-on traction unit with a conventional farm tractor, or other analogous conventional vehicle.
The present invention is concerned with a traction unit that can be added to a conventional farm tractor, in order to increase the tractor mobility in snow, or other soft terrain, e.g., sand or mud. The unit is intended to be installable, on a farm tractor without extensive redesign, or reconstruction of the tractor hardware.